Fig. 2: Device design and characterization.
From: Broadband microwave-rate dark pulse microcombs in dissipation-engineered LiNbO3 microresonators
a Optical microscope images of LiNbO3 microring (left, top) and scanning electron microscope images detailing various components: waveguide-coupled region (left, bottom), the cross-section of the microring waveguide (right, top), and a zoom-in view of the pulley waveguide coupler (right, bottom). The intensity profile of the fundamental TE mode is overlaid on the cross-section. b Integrated dispersion (Dint) of the fundamental TE mode family. The values of D1 and D2 are also listed. c Top panel: normalized transmission spectra of four typical resonances at different wavelengths. Middle panel: broadband transmission spectrum. The fringes caused by the reflection at the bus waveguide facets are removed using Fourier filtering. Bottom panel: measured and simulated total dissipation rates as a function of wavelength. Color shadings represent different coupling conditions. The pump mode and the corresponding Raman gain are also indicated.
